This invention concerns a device to transfer information in motor vehicle traffic between a transmitter-building element associated with a roadway and receivers arranged in motor vehicles of a type in which the transmitter-building element transmits a coded information signal and receivers in the motor vehicles receive and analyze the information signal.
An information system for use by vehicles in a roadway is described in German Offenlegungsschrift DE 36 36 258 A1. With this system, driver information concerning a particular stretch of roadway, for example a speed limit, is suggested to be clearly brought before the eyes of drivers in interiors of vehicles. To accomplish this, traffic indication transmitters are appropriately arranged whose transmitted signals are received and evaluated by vehicles driving past. It is disadvantageous that such transmitters require their own power supplies. Thus, such transmitters require continuous maintenance.
German Offenlegungsschrift DE 39 11 916 A1 describes a process to recognize traffic indications. The apparatus described therein works with a transmitter and a signal identification generator. Each of these is supplied with current by means of a solar generator with a charging regulator and auxiliary battery. In addition to the solar generator a wind generator can be provided. Such an apparatus is quite expensive. Further, structural signal shielding is necessary to guide an information signal to only one vehicle.
In European patent application EP 0 521 846 A1 a wireless signaling system for motor vehicles is described. Also here a dedicated power supply is described for a transmitter. Further, shielding from other vehicles is necessary.
In a publication by the firm AEG, Elektronische Identifikation, a transponder and a read-out device arranged therewith are described. In this device objects in which such transponders are mounted are moved past the read-out device in order to identify the objects. The transponder is provided with a coil to receive a changing magnetic field for creating a changing, or alternating, voltage. The changing voltage provides energy to an integrated circuit in the transponder. The integrated circuit contains a fixed-code in memory as well as logic and a control component. When activated by a magnetic changing field the transponder sends the stored, or memorized, fixed code as a digital code signal. The changing magnetic field is created by a sensing apparatus which is stationary.
In German patent DE 40 03 410 C2 transponders are described for marking, or identifying, animals, for automated production, for cashless payment, and for motor vehicle identification.
According to the state of the art, such transponders are built into a non-stationary part of an information transmittal system.
It is an object of this invention to provide apparatus of the type set forth in the opening paragraph above in which provision of energy to the transmitter-building element is uncomplicated, for which construction costs of the transmitter-building element are low, and for which it is not necessary to employ shielding measures for transmitting signals.